1. Field of the Invention
The present invention relates to a manufacturing method for a dynamic damper.
2. Description of the Related Art
There are dynamic dampers, which reduce vibration of an automobile driving power-transmitting member, such as a propeller shaft, in order to reduce vehicle vibration and mechanical noise. Such dynamic dampers include an outer pipe, a weight disposed inside the outer pipe and an elastic body disposed between the outer pipe and the weight. This dynamic damper is pressed into a hollow shaft constituting the propeller shaft and is fixed thereto.
In the dynamic damper disclosed in Japanese Utility Model Application Publication No. H7-29324, an elastic body is disposed in an annular space between an outer pipe and a weight, and a rod-like elastic interposed portion is provided so as to extend in the radius direction at each of a plurality of positions (five positions) in the circumferential direction of the annular space.
In conventional art, when a dynamic damper is manufactured, rubber is injected into an annular space defined between an outer pipe and a weight such that the outer pipe and the weight have been disposed in a mold to form an elastic body by vulcanization. The elastic body is thereby formed integrally with the outer pipe and the weight.
However, in the rubber injection in the mold, it is difficult to vulcanization-form an elastic body having uniformly even properties along the circumferential direction of the annular space between the outer pipe and the weight. If the spring constants of respective rod-like elastic interposed portions are fluctuated, the resonant characteristic of the dynamic damper is changed, so that a stable damping characteristic cannot be obtained. A mold design and injection are required so that stable vulcanization and cooling of rubber can be obtained. Therefore, the shape of a manufactured product is determined necessarily.